board: rock5b-rk3588: add memory gaps into kernel's DTB

RK3588 has two memory gaps when using 16 GiB DRAM size:
[0x3fc000000 , 0x3fc500000]
and
[0x3fff00000 , 0x3ffffffff]

If the kernel is agnostic to these gaps, accessing the area causes
a SError panic.

Hence, add reserved memory areas in kernel's DTB before booting.

Signed-off-by: Eugen Hristev <eugen.hristev@collabora.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/board/radxa/rock5b-rk3588/rock5b-rk3588.c b/board/radxa/rock5b-rk3588/rock5b-rk3588.c
index b5d7479..5c3b52b9 100644
--- a/board/radxa/rock5b-rk3588/rock5b-rk3588.c
+++ b/board/radxa/rock5b-rk3588/rock5b-rk3588.c
@@ -2,3 +2,38 @@
 /*
  * Copyright (c) 2023 Collabora Ltd.
  */
+
+#include <fdtdec.h>
+#include <fdt_support.h>
+
+#ifdef CONFIG_OF_BOARD_SETUP
+int rock5b_add_reserved_memory_fdt_nodes(void *new_blob)
+{
+	struct fdt_memory gap1 = {
+		.start = 0x3fc000000,
+		.end = 0x3fc4fffff,
+	};
+	struct fdt_memory gap2 = {
+		.start = 0x3fff00000,
+		.end = 0x3ffffffff,
+	};
+	unsigned long flags = FDTDEC_RESERVED_MEMORY_NO_MAP;
+	unsigned int ret;
+
+	/*
+	 * Inject the reserved-memory nodes into the DTS
+	 */
+	ret = fdtdec_add_reserved_memory(new_blob, "gap1", &gap1,  NULL, 0,
+					 NULL, flags);
+	if (ret)
+		return ret;
+
+	return fdtdec_add_reserved_memory(new_blob, "gap2", &gap2,  NULL, 0,
+					  NULL, flags);
+}
+
+int ft_board_setup(void *blob, struct bd_info *bd)
+{
+	return rock5b_add_reserved_memory_fdt_nodes(blob);
+}
+#endif
diff --git a/configs/rock5b-rk3588_defconfig b/configs/rock5b-rk3588_defconfig
index 9b7db7d..f3026c7 100644
--- a/configs/rock5b-rk3588_defconfig
+++ b/configs/rock5b-rk3588_defconfig
@@ -26,6 +26,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_SPL_FIT_SIGNATURE=y
 CONFIG_SPL_LOAD_FIT=y
+CONFIG_OF_BOARD_SETUP=y
 CONFIG_DEFAULT_FDT_FILE="rockchip/rk3588-rock-5b.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y